Question: Solve for $n$ : $n - 9 = 2$
Add $9$ to both sides: $ \begin{eqnarray} \\ n - 9 &=& 2 \\ \\ {+9} && {+9} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{-9 + n} &\hphantom{=}& \hphantom{2} \\ n &=& 2 {+ 9} \\ \end{eqnarray} $ Simplify. $ n = 11$